This invention relates to a method for the electrostatic removal of dust from the exhaust gases of a plant in which raw material, for instance ground cement, is pre-heated with the exhaust gases from a furnace, and the exhaust gases from the pre-heater are subjected to electrostatic dust removal.
Increasingly more stringent demands are being made on the degree of dust removal in the exhaust gases from large production plants, for instance cement factories. The exhaust gases from the pre-heater which need the dust removal frequently are at a temperature between about 310.degree. and 350.degree. C, which is not well suited for electrostatic dust removal.
In order to improve the degree of dust removal, attempts have been made in such cases to lower appreciably the temperature of the exhaust gases by water-cooling (for instance down to a temperature range of about 150.degree. to 170.degree. C). This method cannot however be considered in those cases in which cooling water in sufficient quantities is not available.
It is known that dust removal in an electrostatic filter is considerably improved not only by a drop in the prevailing exhaust gas temperature, but also by an increase in this temperature (to a range for instance of 400.degree. to 420.degree. C). For this reason the efficiency of the pre-heater has hitherto been deliberately reduced by changing its shape, so as to increase the exhaust gas temperature. The main disadvantage of such a method is that the plant is always operating at high heat consumption.